Overview
The serum pH is a measure of the acidity of alkalinity of the blood, based on an inverse log of the hydrogen ion concentration. This can be used in conjunction with the HCO₃ and PaCO₂ to determine whether there is an acid-base disorder present.
Normal Range
- 7.35 - 7.45
Acidaemia
A pH <7.35 is indicative of acidaemia; this may be due to a primary metabolic or respiratory acidosis.
Causes of Acidaemia
- Metabolic acidosis - acid ingestion, lactic acidosis, ketoacidosis, renal failure, renal tubular acidosis, diarrhoea
- Respiratory acidosis - hypoventilation or dead space ventilation
Interpretation
- Reduced HCO₃ ± reduced PaCO₂ - suggests metabolic acidosis
- Elevated PaCO₂ ± elevated HCO₃ - suggests respiratory acidosis
Alkalaemia
A pH >7.45 is indicative of alkalaemia; this may be due to a primary metabolic or respiratory alkalosis.
Causes of Alkalaemia
- Metabolic alkalosis - bicarbonate excess, GI acid loss, renal acid loss, compartmental shift
- Respiratory alkalosis - hyperventilation
Interpretation
- Elevated HCO₃ ± elevated PaCO₂ - suggests metabolic alkalosis
- Reduced PaCO₂ ± reduced HCO₃ - suggests respiratory alkalosis
Next Page
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------